1. Field of the Invention
The present invention relates to rolling bearings.
2. Description of the Related Art
Many rolling bearings are used in various industrial apparatuses. Rolling bearings include an inner ring, an outer ring, a plurality of rolling elements, and a cage. The rolling elements are interposed between the inner ring and the outer ring. The cage holds the rolling elements. For example, as shown in FIG. 7, in a rolling bearing 90 that supports a rotary shaft 95 in a housing 97, an inner ring 91 is fitted on the rotary shaft 95, and an outer ring 92 is fitted to an inner peripheral surface 98 of the housing 97.
In particular, in the case where the rolling bearing 90 is a deep groove ball bearing that is subjected to an axial load in one direction, the inner ring 91 is interference fitted on the rotary shaft 95. On the other hand, the outer ring 92 is often clearance fitted in the housing 97. Accordingly, when the rolling bearing 90 is in use with the rotary shaft 95 rotating, creep (circumferential slipping of the outer ring 92 relative to the housing 97) tends to occur between the outer ring 92 and the housing 97. If creep occurs, for example, the outer ring 92 may damage the housing 97.
As a solution, the rolling bearing 90 is proposed in which an annular groove 93 that restrains creep is formed in an outer peripheral surface 92b of the outer ring 92 (see Japanese Patent Application Publication No. 2006-322579 (JP 2006-322579 A)). This rolling bearing 90 can restrain creep that tends to occur when the rolling bearing 90 is subjected to a large radial load (load in the radial direction). Creep that tends to occur when the rolling bearing 90 is subjected to such a load is such creep that the outer ring 92 slowly slips in the same direction as the rotational direction of the rolling bearing 90.
Such creep can be considered to occur by the following mechanism. When the rolling bearing 90 is subjected to a large radial load, each ball 94 is subjected to the large load and rolls along an outer ring raceway groove 96. At this time, the outer periphery of the outer ring 92 located immediately under the ball 94 is partially elastically deformed. Since each ball 94 rolls along the outer ring raceway groove 96, this causes pulsating deformation (pulsating displacement) of the outer ring 92. This results in relative slipping between the outer ring 92 and the housing 97 due to the elastic deformation of the contact region of the outer ring 92 with the housing 97 (in the case where the annular groove 93 is not formed). This relative slipping is considered to cause such creep in which the outer ring 92 slowly slips in the same direction as the rotational direction of the rolling bearing 90.
Accordingly, such relative slipping is restrained by forming the annular groove 93 in the outer ring 92, whereby creep is restrained. This annular groove 93 is formed based on the fact that the rolling bearing 90 is subjected to a large radial force that causes creep. However, creep need be effectively restrained even when the rolling bearing is subjected to a load containing an axial component as well as a radial load.